Radioactive fluid handling system



March 5, 1963 D. F. RINALD 3,080,307

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March 5, 1963 D. F. RINALD 3,030,307

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United States Patent 01 3,080,307 RADIOACTIVE FLUID HANDLING SYSTEM Donald F. Rinald, Wilkinsburg, Pan, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 21, 1957, Ser. No. 691,264 7 Claims. (Cl. 204193.2)

The present invention relates to a method and arrangement for separating and eliminating radioactive fluids and more particularly to an arrangement and method of the character described associated with a nuclear power plant for separating and delaying or holding up elimination of gaseous fission products until their attendant radioactivity has decayed to tolerable levels.

The invention described herein is adapted, in one application thereof, for use with the radioactive gas absorption system described and claimed in a copending application of Joel Weisman et al., entitlted Gas Handling Systems for Radioactive Gases, filed October 21, 1957, Serial No. 691,263 and assigned to the present assignee.

In connection with previous reactor schemes, it has been proposed to adsorb the radioactive fission gases, in charcoal beds, which when having been saturated, are deposited in shielded burial vaults or otherwise disposed of. This arrangement, however, is feasible for use only with relatively small experimental or research type nuclear reactors wherein only a very small quantity of these fission gases are produced and wherein economical thermal or electrical output is not a primary objective. In the latter instance, however, such an arrangement is extremely expensive even in the case of the smallest nuclear reactors presently in existence or under construction. On the other hand, in the case of a relatively large power reactor, the size of charcoal beds would be prohibitive not only from a monetary standpoint but in regard to space considerations as well.

In other schemes for handling radioactive fission gases an inert carrier gas is added to the radioactive fission gases passing through the charcoal beds and associated components of the gas handling system, from which carrier gaseous fission products are adsorbed selectively by the charcoal or other adsorbent. After passing through the charcoal beds, the carrier gas together with non-adsorbed gaseous fission product isotopes is vented to the atmosphere or alternatively is compressed for underground or oceanic disposal. In the latter arrangement relatively large quantities of the longer-lived fission gases together with the carrier gas must be either vented to the atmosphere or stored, which, of course, results in the necessity for providing increased storage and handling capacity. Moreover, in the case where the non-adsorbed fission gases are vented to the atmosphere, operation of the gas handling system in this manner is extremely difficult in the case of the larger power reactors because of imposed limitations upon the amount of radioactivity which can be discharged in this manner. In any case, the usage of the carrier gas in this manner results in complete loss of the carrier gas once it has been added to the gas handling system. However, use of a carrier gas is essential due to the relatively large volumes associated with the components of the radioactive gas handling system and the very much smaller volumes of the fission product gases. Moreover, the employment of a once-through charcoal bed adsorption system requires a comparatively large quantity of charcoal.

The present invention contemplates a radioactive gas 3,080,307 Patented Mar. 5, 1963 "ice handling system such as a gaseous fission product elimination system, or olf-gas system, which permits adequate decay of the fission gases and resultant venting thereof to the atmosphere and also reuse of the charcoal beds. Moreover, the invention in certain cases permits usage of much smaller charcoal beds than otherwise would be required. During the forthcoming description of the illustrative arrangements of the invention, the off-gas system will be described in connection with a quasi-homogeneous reactor plant employing deuterium oxide or heavy water carrier. It will be obvious, however, as this description proceeds that the oil-gas system of the invention can be adapted with equal facility to other types of neutronic reactor systems and to fuel processing plants or other plants handling radioactive gases.

In order to comprehend properly the scope of the invention it should be borne in mind also that the terms adsorption, absorption, adsorbent, adsorbed and the like are intended, as used herein, to denote in addition any reasonable equivalent thereof without regard to the particular form of sorption phenomenon that may be involved.

In view of the foregoing, an object of the present invention is to provide a novel and efficient radioactive gas handling system and more particularly an oil-gas system adapted for use with a nuclear power plant.

Another object of the invention is to provide an improved carrier gas system adapted for use in conjunction with the aforementioned radioactive gas handling system.

A further object of the invention is to provide a radioactive gas handling system adapted for furnishing increased hold-up time before venting the radioactive gases to the atmosphere or to other disposal means.

Still another object of the invention is to provide a gaseous fission product elimination system which is adapted for use with a neutronic reactor plant or a nuclear fuel processing plant and which is capable of holding up elimination of these gases in order to permit radioactive decay thereof to acceptable energy levels before disposing of these gases.

Another object of the invention is to furnish an improved radioactive gas handling system adapted for separating the gases into groups of shorterand longer-lived isotopes in a novel manner.

A still further object of the invention is to provide an improved radioactive gas handling system in which the consumption of carrier gas employed therein is minimized.

Yet another object of the invention is to provide an improved radioactive gas handling system wherein means are provided for reducing the quantity of charcoal or other adsorbent employed in the gas handling system.

Another object of the invention is to provide an improved gas handling system, adapted for use with a neutronic reactor, wherein means are provided for selectively and immediately removing from the system those radioactive gaseous fission products which have a relatively high neutronic capture cross section, and for permitting recirculation through the gas handling system those gaseous fission products whose neutronic adsorption characteristics are negligible.

Still another object of the invention is to provide a gas handling system adapted for separating and eliminating radioactive gases to the atmosphere or other disposal means and having means associated therewith for holding up the 'gases in the event adverse weather conditions or other contingency preventing continuous usage of the dis posal means.

tablished in the vessel.

These and other objects, features, and advantages of the invention will be made apparent during the forthcoming description of illustrative forms of the invention, with the description being taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a schematic and elevational view, partially sectioned, of one form of reactor vessel and associated primary components adapted for use with a homogeneous or quasi-homogeneous reactor;

FIG. 2 is a schematic fluid circuit diagram of the homogeneous reactor illustrated in FIG. 1 as arranged in connection with certain auxiliary equipment;

FIGS. 3A and 3B depict a schematic fluid circuit diagram of a radioactive =gas handling'system which depicts in greater detail the gas handling system denoted generally by the reference characters 78, 80 and 90 of FIG 2;

FIG. 4 is a graphical representation showing one methd of operating the charcoal beds illustrated in FIGS. 3A and 3B in order to obtain optimum conditions of decay and adsorption of fission gases when the gas handling system of FIGS. 3A and 3B is employed in conjunction with the reactor system described hereinafter more fully with reference to FIGS. 2, 3A and 3B of the drawings;

FIG. 5 is a graph showing the heat of radioactive decay of various gaseous fission products as plotted against time after fission;

. FIG. 6 is \a quantitative schematic fluid circuit diagram showing the relative amounts of radio-active and other gases handled by a portion of the gas handling system;

FIG. 6a is a legend indicating the differinggases and vapors handled by the off-gas system of the invention; and

FIG. 7 is a graphical representation of equilibrium ratios for the adsorption of krypton and xenon on charcoal based on data supplied by J. M. Holmes, Design of an Adsorber," OR=NL CF-51-6-70.

Generally speaking, in a homogeneous-type reactor system, the nuclear fuel is contained within the system as a liquid or suspension which in some cases may be a liquid compound of at least one of the fissile isotopes noted below. In other cases, the liquid fuel comprises a suspension in a suitable vehicle of a pulverulent form of one or more of these fissionable and fertile isotopes, or

combination, thereof, of a solution of at least one of these components. In those systems wherein the fuel is employed as a suspension or slurry, the reactor system is sometimes designated as quasi-homogeneous. As explained more thoroughly hereinafter, the liquid fuel is circulated through a reactor vessel by one or more primary circulating loops. provided with suitable pumping means. The liquid fuel including the vehicle or solvent, which desirably serves both as coolant and moderator,

thus circulates through both the vessel and the circulating loops in contradistinction to a heterogeneous type reactor system. In the latter class of reactors the fuel, moderator, and the coolant or coolant-moderator usually are physically separated and at least the tuel is contained in solid form entirely within the reactor vessel.

The homogeneous reactor vessel is fabricated of such size and shape that a quantity of the circulating liquid fuel containedtherein is equivalent to the critical mass of the chain reacting isotope contained in the fuel and consequently a self-sustaining chain reaction can be es- In the caseof a quasi-homogeneous reactor, the concentration of the fissionable or chainreacting isotope in the slurry or suspension can be adjusted within rather wide limits such that the "aforesaid size and shape of the vessel can be varied accordingly as desired. As pointed out hereinafter, the remaining components of the system are insufiicient in size and are suitably spaced or shielded such that a critical mass cannot be accumulated elsewhere in the reactor system.

Theheat developed Within the circulating fuel as a result of the nuclear chain reaction is removed from the fuel 4 as it circulates through the primary loops by suitable heat exchanging means coupled within each of these loops.

The vehicle or solvent employed with the circulating fuel, which may be ordinary water (H 0), heavy water (D 0) or an organic material having the desired characteiistics of temperature and radiation stability, serves as a moderator for the chain'reaction in addition to serving as a heat transfer medium as noted heretofore. As is well known, a moderator material usually is employed adjacent the nuclear fuel to slow the fast neutrons produced by each fission to thermal velocity, wherein the neutrons are most eflicient for inducing fission in atoms comprising the fissionable isotopes. More specifically, the moderator material 'slows neutrons having energies in the neighborhood of ten million electron volts to energies which are equivalent to thermally excited hydrogen atoms or about 0.1 electron volt. As a result, the moderator material appropriately is selected from a material having the characteristics of low neutronic capture crosssection and a high neutronic scattering cross section. Suitable materials for these purposes include carbon and the vehicles or solvents noted heretofore, i.e., light and heavy water, and hydrocarbon organic materials which, of course, contain carbon and hydrogen.

The homogeneous reactor system, presently to be described, is controlled inherently by the negative temperature coefiicient of reactivity associated with the circulating nuclear fuel. This phenomenon is comparatively well known and is based upon the fact that an increase in temperature of the fuel contained within the reactor vessel decreases the density of the vehicular moderator and likewise its moderating characteristics. By the same token, this decrease in density increases the number of peripheral neutrons lost from the chain reacting mass and accordingly lowers the numbers of neutrons available for sustaining the chain reaction. Additional control is accomplished, as required, 'by diluting the circulating fuel with additional vehicle or solvent, by adding a neutron absorbing poison such as cadmium or boron, or by draining the contentsof the reactional vessel into a series of storage tanks presently to be described. The latter arrangement -also serves to terminate the chain-reaction completely in an emergency or to shut down the reactor for maintenance and-the like.

The fission products which are formed during operation of the reactor must be extracted continually from the system by means of chemical processing in the case of solids, or in thecase of gases, by means of an ofi-gas system such that'forming the subject of the present invention. These fission products cannot be permitted to accumulate within the reactor system inasmuch as some of the isotopes, particularly xenon 135, eventually terminate or poison the chain reaction although present in relatively small concentrations. In any event, the accumulation of these isotopes which result either directly, or indirectly through radioactive decay, from the fission process would in time greatly increase that radioactivity necessarily associated with the reactor plant even though the fission products are removed continuously. As a result, the normal biological shielding requirements would be greatly increased. Moreover, many of the fissionproduced isotopes are valuable per se 'for those research, industrial, and medicinal applications which demand ahigh level of various radioactive emanations.

During the progress ofrhe chain reactiomeach fissioned atom emits an average of two to threeneutrons. Approximately one of these neutrons is utilized in propagating the chain reaction. Another one of the neutrons is employed to initiate one of the series of nuclear reactions described 'below, whereby an atom of the fertile or blanket material transmuted into fissionable isotope equivalent, for example, to the amount of fiss'ionable material consumed in thechain reaction. If such is the case, only fertile material need be "added to the homogeneous reactor system during its operation. The remainder of the fission-produced neutrons are absorbed in structural and moderator materials and 'm non-fissioning capture by atoms of fissile material or are lost from the periphery of the chain reacting mass.

In conversion type homogeneous reactors, an additional quantity of a fertile isotope such as Th or U is mixed with the circulating fuel material. The latter fertile isotope can be supplied in the form of natural or source grade uranium which is primarily the U isotope admixed With approximately 0.7% of U In a heterogeneous type reactor, the same combinations of fissionable and fertile isotopes can be employed, with the except-ions that both groups of the fissile isotopes are fixedly mounted within the reactor core and that the fertile isotope, commonly referred to as blanket material, usually surrounds the fis'sionable material. However, in a uniform, w enrichment heterogeneous reactor, several designs of which are either extant or under consideration, the so-called blanket or fertile material, of course, is mixed uniformly with the fissionable isotope. In the latter class of reactors, U usually is employed which has been enriched to a greater than natural percentage of U In an efficient react-or of the previously-mentioned regenerative types, it is possible to generate from the one or more fertile isotopes at least as much fissionable isotopes as is consumed in the chain reaction. if the conversional ratio is greater than unity, the reactor is classified in the breeder category.

Upon capturing one of the aforesaid neutrons the fertile material U if employed, is converted into the transuranic element, plutonium .;Pu in accordance with the following nuclear equations:

A zas 1 13235 ass 1 259 23 mm. d

The resultant fissionable isotope U having a half-life of 163,000 years, likewise is relatively stable.

Referring more specfically to FIGS. 1 and 2 of the drawings, the homogeneous reactor system comprises a reactor vessel 29 having a spheroidal configuration and provided at diametrically opposite areas thereof with inlet and outlet manifolds 22 and 24, respectively. The reactor vessel 2i} is of suificient size to contain, as aforesaid, a critical mass of the circulating nuclear fuel flowing through the vessel and the primary loops of the reactor system. In this application, wherein a circulating slurry containing suspended pulverulent oxides of thoriurn (ThO and highly enriched uranium U0; is employed, with a vehicle including deuterium oxide or heavy water (D 0), the inside diameter of the innermost reactor vessel thermal shield 40 is of the order of 13 feet. The aforementioned slurry thus includes a fissionable material in the form of uranium 235 and a fertile material, thorium 232. Additionally, a small proportion of the fertile material, uranium 238, is included unavoidably with the U isotope.

In this example of the homogeneous reactor system, a total of four circulating loops are connected to the intake and outlet manifolds 22 and 24- by means of inlet and outlet conduits 26 and 28, respectively. The outlet conduit 28 is connected to a gas separator 30 which in turn is coupled in series with a steam generating heat exchanger 32 coupled through a conduit 35 to the suctional side 34 of a primary slurry pump as. The gas separator 3% is furnished in a conventional design and is arranged to remove fissional and radiolytic gases from the system which gases are conducted out of a separator by means of a conduit 31. The steam generator 32 which is provided inter alia with a feed water inlet 33 and a steam outlet conduit 37 is fabricated in the form such as that described in a copending application of William A. Webb et al., entitled Remote Equipment Maintenance, Serial No. 659,002 filed May 14, 1957, now abandoned, and assigned to the present assignee. The discharge side of the pump 36 is coupled to the intake conduit 26 and manifold 22 of the reactor vessel.

In this example, the reactor vessel 26 is formed from a plurality of spheroidal sections 38 which are welded together as shown to form the completed vessel. In order to minimize thermal stresses within the walls of the vessels Zfl, which are of the order of six and one-half inches in thickness, a plurality of thermal shields, indicated generally by the reference character 4i are disposed adjacent the inner surface of the reactor vessel walls. The thermal shields i6 conform generally to the inner configuration of the vessel walls and are spaced therefrom and from one another in order to provide, in this example, channels therebetween for passage of the circulating nuclear fuel. Inasmuch as the thermal shields 40 are subjected to little or no pressure differentials, they are made relatively thinner with respect to the vessel walls 20. A plurality of bafiles 42. are disposed adjacent the lower or intake manifold 22 and are suitably shaped for distributing the incoming slurry as indicated by flow arrows 44 throughout the interior areas of the vessel 26} and for diverting a peripheral portion of this flow through the passages formed between the thermal shields 4i] and adjacent the inner wall of the vessel 20. A neutron reflecting member (not shown) can be disposed adjacent the thermal shields to reflect peripheral neutrons back into the central region of the vessel 20 in order to improve the neutron economy of the chain reaction.

The disposition of the thermal shields 49 in this manner substantially prevents impingement of fission-neutrons upon the adjacent vessel walls. Accordingly, the heating effect of the impinging neutrons is developed almost entirely within the thermal shields 46 which are not subject to pressure stresses as are the walls of the pressurized vessel 24 Moreover, the heat developed within the thermal shields it} is readily removed by that portion of the circulating fuel flowing through the channels therebetween. Alternatively, the thermal shields 40 can be replaced by the shield arrangement (not shown) disclosed and claimed in a copending application of W. P. Haass, entitled Reactional Vessel, Serial No. 652,627, filed April 12, 1957, and assigned to the present assignee.

The pressurized reactional vessel 20 is mounted upon an annular supporting collar indicated generally by the reference character 46 and mounted upon the biological shielding wall portion or support 48. This mounting arrangement for the reactor vessel 20 and the physical distribution of the primary circulating loops and other equipment associated therewith is described in greater detail in a copending application of W. A. Webb et al., entitled Reactor Plant, Serial No. 659,004, filed May 14, 1957, and assigned to the assignee of the present application.

In order to drain the reactor vessel, a drain outlet 50 disposed in the lower or intake manifold 22 is coupled to a series of slurry drain tanks 52, through a conduit 54. When it is desired to fill the reactor system, the slurry contained in the drain tanks 52 is returned through another conduit 56 which is coupled to one or more of the circulating loop conduits 35. To aid in filling the reactor Vessel and associated loops, an auxiliary slurry pump 58 is coupled into the conduit 56. The physical disposition of the drain tanks 52 relative to the nuclear critical mass of the circulating fuel.

trated schematically therein.

power plant layout arrangement is described in greater detail in the last-mentioned copending application. For the present, it may be pointed out that the drain tanks 52 are provided in sufiicient number to contain all of the circulating nuclear fuel slurry of the system but are of such size that none of the tanks can contain a critical mass of slurry. Suitable neutron-absorbing material (not shown) is disposed between adjacent tanks in order to prevent the development of a chain reaction within the collective group of tanks when they are filled with the circulating fuel.

In one exemplary arrangement, the fluid fuel contained within each of the drain tanks 52 is stirred constantly by individual agitators or stirrers 59 mounted adjacent the top of each of the tanks 52. The tanks 52 and the agitators 59 desirably are hermetically sealed to prevent leakage of biologically hazardous fluid and desirably are provided in the form of that disclosed and claimed in a copending application of Mei and Widmer, entitled Sealed Agitator, Serial No. 672,661, filed July 18, 1957, now US. Patent No. 2,907,556, and assigned to the present assignee.

The upper or outlet header 24 is fitted with an additional port '60 to which a surge tank 62 is coupled by 'means of a conduit 66. In one form of homogeneous reactor system, the surge tank 62 comprises a relatively large volume which, however, is insufficient to contain a When in operation, a vapor space 68 is formed in the surge tank, which conveniently contains a vapor of the vehicle employed in suspending the aforementioned fissionable and fertile oxides. As a result, during a positive system transient within the homogeneous reactor system, a surge of liquid into the tank 62 compresses the vapor confined within the surge tank space 68, thereby relieving at least partially the increased pressures developed within the system.

A pressurizing vessel 64, which is coupled to the tank 62 by a conduit 67 connecting the vapor spaces thereof, is furnished with a number of heating elements, indicated generally by the reference characters 70 and arranged for heating a portion of liquid, desirably the same as the aforementioned liquid vehicle of the system. Thus, the reactor system is maintained at the desired operating pressure, by vaporization and expansion of the aforesaid vehicle portion. The pressurizing vessel 64 is provided with an inlet conduit 72 whereby the vessel is initially charged with the aforesaid vehicle portion and make-up vehicle is added to the pressurizing vessel as required. This make-up vehicle is necessitated by radiolytic decomposition of the vehicle within the system and the incomplete recombination of the component gases of the vehicle.

Alternatively, the pressurizing vessel 64 and the surge tank 62 can be replaced by the pressure regulating system claimed and disclosed in a copending application of Jules Wainrib, entitled Pressure Controlling System, Serial No. 677,942, filed August 13, 1957, now US. Patent 3,060,110 and assigned to the present assignee.

Referring now more particularly to FIG. 2 of the drawings, various auxiliary equipment associated with the aforedescribed homogeneous reactor system, is illus- In the arrangement of the homogeneous reactor system, illustrated in FIG. 2, the primary slurry pump 36 is furnished with a capacity of approximately 8,000 gallons per minute which in conjunction with three other primary slurry pumps (not 'shown) disposed in a like number of similar circulating loop systems indicated generally by arrows 74, produces 'a total rate of flow of approximately 32,000 gallons per minute. Inasmuch as the reactor vessel 20 and the circulating loops together enclose a total volume of approxi- W mately 19,000 gallons, the circulating fuel is recycled through the system in about one-half minute.

In this application of the invention, the circulating slurry comprises a vehicle of deuterium oxide (D in which is suspended about 300 grams of thorium oxide 8 (T110 per kilogram of D 0 and approximately ten grams of uranium U0 per kilogram of D 0. The uranium is fully enriched and contains upwards of of U isotope. Added with the uranium oxide is a very small proportion of a palladium catalyst employed to promote in this example internal recombination of the major proportion of the radiolytic vehicle gases deuterium and oxygen. The uncombined or remaining radiolytic gases are employed to sweep fission product gases out of the system, as explained hereinafter. The quantity of palladium catalyst, which is added in the form of the oxide (PdO), is of the order of 0.001 gram per liter of slurry and can be replaced by another suitable catalyst, such as a platinum compound.

Accordingly, the system circulates a mixed oxide slurry with a total oxide concentration in excess of 300 grams per kilogram of D 0 which corresponds to a solids content of about 3% by volume. The reactor vessel 20 and the circulating loops 74 are maintained under a pressure in the neighborhood of 2,000 pounds per square inch absolute by operation of the pressurizing vessel 64. The pressurizing vessel 64, which desirably contains only deuterium oxide or other such vehicle, employed in the homogeneous system as noted heretofore is separated from the liquid or slurry portion of the surge tank 62 by means of the steam space 68 thereof, to which the conduit 67 is coupled, thus avoiding the caking that would result if the circulating slurry itself were boiled in the pressurizing vessel 64.

Leaving the reactor vessel the slurry stream branches into four parallel identical circulating loops 74 only one of which is illustrated in detail. If desired, each loop can be isolated from the reactor by providing two pairs of dual stop valves 76 to permit certain types of remote or semi-direct maintenance to be performed on one of the circulating loops without shutting down the entire plan-t. Such maintenance can be performed, for example, in the manner described in the aforesaid copending application of McGrath et al., Serial No. 659,003, and in a copending application of Webb et al., Serial No. 659,002, filed May 14, 1957, now abandoned, entitled Remote Equipment Maintenance, and also assigned to the present assignee.

Within the reactor vessel 20, part of the kinetic energy of the fission fragments is absorbed by the deuterium oxide molecules some of which are disassociated into deuterium and oxygen gases, which for the most part are combined within the reactor system through usage of the palladium catalyst noted above. However, the remaining portion of these radiolytic gases is recombined by means of an external recombining unit, indicated generally by the reference character 78 and described in greater detail in connection with FIGS. 3A and 3B of the drawings wherein the gases are recombined through the use of a suitable external catalytic agent, such as platinum.

Returning now to FIG. 2 of the drawings, the unit 78 is coupled through a conduit 79 to the outlet of a gas letdown or depressun'zing device 80, which in turn is connected to the conduits 31 of the gas separators 30. In this arrangement, the depressurizing device is adapted for handling the gases extracted from the primary loops by the gas separators 30, after the entrainment has been removed. The slurry entrained in the gas separator output is separated by equipment associated with the depressurizin-g device and described in greater detail in connection with FIGS. 3A and 3B, and is returned to the suctional side of the primary slurry pump 36 by means of a conduit 82. The pure deuterium oxide compounded from the radiolytic gaseous components thereof at the recombining unit 78' is conducted from the unit through outlet '84 and suitable conduits to the primary slurry pumps 36, the auxiliary pump 58, and valves 76 for purging purposes and other applications described hereinafter. The total deuterium oxide formed in the recombining unit is in the neighborhood of 1,600 pounds per hour'at full power and assuming 90% internal recombination by means of the aforesaid palladium catalyst. A portion of this output is added to the pressurizing vessel 64 by means of its feed water inlet 72. The pr-essurizing vessel feed water or make-up vehicle is in the order of 100 pounds per hour of deuterium oxide.

The uncondensed gases issuing from the recombination unit 78 through a conduit 83 are delivered to an offgas system -90 whereat a quantity of a suitable vehicle, such as ventilation air taken from the reactor plant arrangement presently to be described, is mixed with the radioactive uncondensed gases in order to dilute these gases, for example, the longer-lived radioisotopes of krypton and xenon, before venting the same to the surrounding atmosphere. Before mixing with the ventilation air, these gases are held up in charcoal beds, presently to be described, until their radioactivity has decayed to a minimum value. Any deuterium oxide which is recovered in the off-gas system 90 is returned through a conduit 92 to the recombination unit 78 where it is combined with the deuterium oxide output thereof.

For purposes of reprocessing or purifying the circulating fuel, a very small and not necessarily constant stream of the order averaging 18 pounds per hour is bled from one of the primary circulating loops 74 and is conducted through a conduit 94 to a slurry-letdown or depressurizing arrangement 96. In the slurry-letdown system, a sustantial amount of system pressure is removed from the slurry and at the same time it is cooled to prevent fiashing. The letdown device 96 comprises a length of small diameter coiled tubing (not shown) or other pressure dropping device, immersed, for example, in a tank of coolant fluid. The slurry is then concentrated by evaporation or settling, and the vehicle or diluted slurry is returned to the suctional side of the primary slurry pump 36 by means of a conduit 98. The conduit 98 desirably joins the outlet conduit 56 of a slurry draining and filling system, indicated schematically at 100, and thus is returned to the primary circulating loop by means of the auxiliary slurry pump 58. For purposes of initially filling the reactor system, the auxiliary slurry pump 58 and conduit 56 are bypassed by a conduit 102 connecting the drain tanks 52 (FIG. 1) of the slurry handling system 100 directly to the suctional side of the primary pump 36 whereby, in this example, the latter pump can draw the homogeneous reactor fuel directly from the drain tanks 52.

The concentrated slurry output of the slurry letdown system 96, which is now maintained at a lower pressure suitable for chemical reprocessing is conducted through a conduit 104 to a chemical reprocessing plant 106 which is arranged exteriorly of the vapor container (not shown) associated with the nuclear power plant but which is nevertheless, integrated therewith. In the chemical processing plant, the fission products are removed and the reprocessed slurry is returned to one of the primary circulating loops through an outlet conduit 108, the conduits 98 and 56, and the auxiliary slurry pump 58. The liquid and solid wastes separated from the concentrated slurry are conveyed through a conduit 110 to suitable storage chambers to await suficient decay thereof in the case of shortlived radioactive materials or for underground or oceanic burial in the case of long-lived materials. Additional fertile material is added to the reactor system by means of a conduit 111, whereby the material desirably is mixed with the reprocessed slurry. Another conduit 112 is provided for conducting radioactive gaseous materials separated in the chemical processing plant to the off-gas system 90. These gaseous materials, of course, consist of residual fission product gases which were not removed by the gas separators 30 for subsequent treatment in the gas handling system, presently to be described.

In the operation of the homogeneous reactor system, approximately 19,000,000 pounds per hour of the circulating nuclear fuel suspension or slurry enters the reactor vessel 20 at a temperature of approximately 465 F. As the chain reaction proceeds within the reactor vessel 20, with the deuterium oxide vehicle of the slurry acting as a moderator therefor, the temperature of the circulating fuel issuing from the top or outlet manifold 24 of the vessel is increased to 580 F., at a maximum power output. With the arrangement shown, approximately 550 megawatts of heat is developed by the reactor system of which in one application, approximately 25% is converted to electrical energy by a suitable thermodynamic arrangement (not shown). As explained heretofore, the circulating fuel is divided into four streams which are conducted respectively to the four steam generators 32' where the heat developed in the reactor vessel 20 is given up to ordinary water maintained in the steam side of the generator to form a total of approximately 2,000,000 pounds per hour of steam at a pressure in the neighborhood of 400 pounds per square inch absolute. This output from the four steam generators is conducted, for an example, to a turbine (not shown) through the steam outlet conduits 3 7 from which turbine the spent steam or condensate is returned through the feed water inlets 33 to the individual steam generators.

Referring now to FIGS. 3A and 3B of the drawings, the gas letdown system 80, the recombiner 7 8, and the off-gas system are illustrated in greater detail. During operation of the reactor 20 the output from the four gas separators, represented in FIG. 3B by the reference character 30 and outlet lines 31, is conveyed to a slurry entrainment separator 122. For the reactor system illustrated in FIGS. 1 and 2, the composition tabulated below is conveyed to the slurry entrainment separator under substantially the conditions existing at the gas separators 30, that is to say, at a pressure 2,000 pounds per square inch absolute and a temperature of approximately 580 F. These conditions of temperature and pressure are substantially those at which the reactor circulating loops described heretofore are operated. The following quantities are the anticipated maxima for design purposes and therefore are based upon full reactor power output and the absence of internal recombination of the radiolytic gases:

Gas or other component: Quantity per minute, pounds The slurry separated by means of the entrainment separator 122 is returned to the suction side 34 of a single one of the primary circulating loop pumps 36 (FIGS. 1 and 2), through a conduit 124, a control valve 126, and a check valve 128. The check valve 128 is furnished to prevent any reverse flow of primary slurry to the separator 122 in the event of pump failure. The remainder of the materials fed into the slurry entrainment separator 122 are conducted through conduit 130 to a second entrainment separator 132, with a flow regulating valve 134 being coupled in the conduit 130. The pressure of the output material of the slurry entrainment separator 122 is reduced from the reactor system operating pressure of 2,000 p.s.i.a. to 100 p.s.i.a. by means of the lines or conduits 133 and valves 135 which comprise a pressure letdown device. More specifically, this device includes a number of small diameter pipes 133 connected in parallel each having a control valve 135. Thus, the letdown device controls the flow to the recombiner 154 presently to be described and reduces the pressure of the slurry entrainment separator output to that of the evaporator 138 or 100 p.s.i.a.

The liquid deuterium oxide vehicle, amounting to 944 pounds per minute, which is separated by the entrainment separator 132 is conveyed through a conduit 136 to an evaporator 138. The evaporator 138 is furnished with a heated bottom leg or conduit 140, with which is 1 1 associated a heating element 142. Heat is supplied to the element 142 by means of process steam (H O) which is conducted thereto through a conduit 144 and valve 146. In this example, 1,821 pounds per minute of the process steam is utilized, with the steam being supplied at 400 F.

under a pressure of 250 p.s.i.a. The process steam condensate is then removed from the heating element 142 to a suitable drain by means of a conduit 148. The vaporized D steam which is produced within the evaporator 138 is conducted back to the entrainment separator .132 through a conduit 150. By this arrangement, the D 0 steam serves as a diluent -for the deuterium and oxygen gases which leave the entrainment separator by means of an overhead conduit 152. This diluent is necessary in order to control the chemical reaction between the deuterium and oxygen which is subsequently carried out in a recombiner 154.

An additional quantity of liquid D 0, amounting to 1,100 pounds per minute, is conveyed to the evaporator heating leg 140 through conduits 155 and 168 and flow control valve 157 from the D 0 storage tank 160 through the recombiner heat exchanger 158. The latter portion of D 0 likewise is converted to diluent steam in the evaporator 138 and is supplied thereto from the high pressure heavy water storage tank 160, in a manner presently to be described. Still another quantity of diluent D 0, 1,267 pounds per minute, is supplied to the output of the slurry entrainment separator 12 2 from the same source through the valved conduit 159. Each of these quantities of liquid D 0 are furnished at a temperature and pressure of 580 F. and 2000 p.s.i.a., respectively. As a result of this dilution, the following quantity of material is supplied to the recombiner 154 during each minute of reactor operation: 54 pounds of deuterium, 218 pounds of oxygen, 3,414 pounds of D 0 vapor, and the quantity of fission product gases noted heretofore.

The recombiner 154 is provided with a start-up heater 156 which has an electrical capacity of about 34 kilowatts. After the chemical reaction between the deuterium and oxygen is initiated in the recombiner 154, the heat revolved by the reaction is removed by means of a recombiner heat exchanger indicated schematically by the reference character 158. The heat of the deuteriumoxygen reaction is limited to about 1100 F. by means of the diluent D 0 noted heretofore and by the heat exchanger 158. This heat is employed to heat high pressure "deuterium oxide which is withdrawn from a high pressure D 0 storage tank 160 through the conduits 162 and 164. 3,641 pounds per minute of liquid D 0 is supplied to the heat exchanger 158 at a pressure of 2000 p.s.i.a. and at a temperature corresponding to that of the high and low pressure storage tanks 160 and 180 or 210 F. In the heat exchanger 158, this quantity of D 0 is raised 'to a temperature of 580 F. which, of course, is not suffi- 'cient to boil the D 0 at this pressure. Portions of this D 0 are then conveyed to the heating leg 140 of the evaporator 138 through conduits 168 and 155, and to the slurry entrainment separator output conduit 130 through conduits 168, 159 and 166 as described above. A third portion, or 1,273 pounds per minute of the recombiner heat exchanger 158 is output supplied to the surge line 66 (FIGS. 2 and 3B) through conduit 169 and flow control valve 171, whereby make-up D 0 vehicle is added to the circulating loops 74 '(FIG. 2). As indicated heretofore, all of the recom-biner heat exchanger output including the make-up vehicle, is maintained at 580 F. and 2000 p.s.'i;a., which correspond to the temperature and pressure, respectively, of the slurry exiting from the reactor vessel 20 through the outlet conduits 28 (FIG. 1). A check valve 173 is coupled in the conduit 169 to prevent reverse or surge flow of slurry through this conduit.

A very small side stream is extracted from the conduit 168 and is conveyed through conduit 177 and the feed water conduit 72 of the pressurizer 64 (FIGS. 1 and 2) Tw'her'e it serves as make-up"forthe'pressurizing vessel 64.

Thus, the pressurizer make-up likewise is delivered at a temperature of 580 F. and 200-0 p.s.i.a., which are the reactor vessel output operating conditions, and the valve in the conduit 177 is adjusted, in this example, to permit a flow of 1.4 pounds per minute of liquid D 0 in order to maintain a constant water level in the pressurizer 64.

The gases and vapor issuing from the other side of the recombining heat exchanger 158 at 40 p.s.i.a. and 280 F. are conveyed through a conduit 172 to a recombiner condenser 174. The material condensed in the recombiner condenser 174 is then conducted through a valved conduit 176 to a cooling unit 178 wherein the condensed D20 is cooled sufliciently for induction into a low pressure deuterium oxide storage tank 180. The liquid output of the condenser 174 exits at 35 p.s.i.a. and 260 F., but in the cooling unit 178 its temperature and pressure are lowered to 210 F. to prevent vapor binding of the high head purnps 184. From the storage tank 180 the liquid deuterium oxide is conveyed through a conduit 182 to a system of high head pumps, one of which is indicated generally by the reference character 184. The pumping system 184 serves to increase the pressure of the deuterium oxide to the operating pressure of the reactor system or 2000 p.s.i.a. The output of the pumping system 184 is conveyed through a conduit 185 and the conduits 162 and 164, respectively, for storage in the high pressure tank 160 or for heating in the recombining heat exchanger 158 from which it is subsequently introduced into the reactor system as described heretofore. Any vapor developed in or conveyed to the low pressure deuterium oxide storage tank 180 is conducted through a valve-d conduit 186 for recirculation through the recom-biner condenser 174, from which it is then returned through the conduit 176 and the cooler 178 in the manner described heretofore.

The gases withdrawn from the heat exchanger 158 through the conduit 172 are thus conveyed to the recombining condenser 174 at a substantially lower pres sure. For this reason, the aforementioned high head pumps 184 are coupled between the low pressure storage tank 180 and the high pressure storage tank 160. The liquid deuterium oxide removed from the recombiner condenser 174 through the conduit 176 has been further cooled to 260 F. and a corresponding pressure of 35 p.s.i.a. by the cooling water supplied to the condenser 174 through the conduits 188 and 190. In the cooler 178 the temperature is further lowered to the operating temperature of the storage tank 180 or 210 F. At this temperaturmof course, the low pressure storage tank 180 can be maintained substantially at atmospheric pressure if desired, but in this example the liquid deuterium oxide is maintained at a pressure of about 35 p.s.i.a. within the low pressure tank 180 in order to avoid the possibility of vapor binding in the high head pumping system 184 when D 0 is pumped into either the reactor system or the high pressure storage tank 160, both of which are maintained at an operating pressure of about 2000 p.s.i.a.

An inert carrier gas, such as nitrogen or helium, is supplied to the recombiner condenser 174 through a valved conduit 192 from a carrier gas storage tank 194. The carrier gas is supplied to the storage tank 194 by means of a centrifugal pump or blower 196 through a conduit 198 and check valve 200. The pump 196 is thus employed to withdraw the carrier gas from suitable storage cylinders (not shown) through a suction conduit 202. The carrier gas which is supplied to the recombiner condenser 174 is employed to flush the uncondensed fission products and other-gases out of the recombiner condenser 174 and subsequent components of the gas handling system. As explained hereinafter more thoroughly, the carrier gas is recycled through the gas handling system in order to conserve the carrier gas, to provide additional hold-up means for the radioactive gases particularly in the event ofinc'lement'weather or the absence of other means.

suitable disposal means, and in addition to ensure proper adsorption of the radioactive gases.

The separation of non-condensible or noble gases from the deuterium oxide condensate in the recombiner condensate leaves at the lower end. The non-condensed or noble gases collect in the upper end of the condenser 174 whence they are conveyed to the gas handling components presently to be described. This arrangement also minimizes the amount of Xenon poison dissolved in the condensate leaving the condenser 174, which condensate eventually is added to the reactor system as make-up fluid in the manner described previously.

Additionally, a small amount of liquid droplets of deuterium oxide are likewise carried out of the condenser 174. The uncondensed gases, carrier gas, and the liquid droplets or mist are conducted to a mist collector or entrainment separator 204 through the valved conduit 2W5. The mist collector 2&4, together with the aforementioned slurry entrainment separator 122 and the separator 132, is conventional in construction and desirably includes a cyclone type separator or other centrifugal separating The entrained deuterium oxide separated from the fission product gases in the mist collector 204 is conducted through an outlet conduit 2% and check valve 210 to the outlet conduit 176 of the recombiner condenser 174. Thus, the outputs of the mist collector and recombiner condenser are combined for cooling and storage in the cooling unit 178 and the low pressure tank 180, respectively.

After removal of the D mist or liquid droplets, the gaseous output of the mist collector 264 is conducted through a conduit 212 (FIGS, 3A and 33), a check valve 214 (FIG. 3A), and a flow control valve 216 to a radiation facility denoted generally by the reference character 218. The aforesaid mist collector gaseous output consists in this example, of 0.136 pound per minute of uncondensed D 0, 3.7 pounds per minute of gaseous fission products, and 8.33 x l()' pounds per minute of the carrier gas, and is exited at a temperature of 259 F. and a pressure of 35 p.s.i.a. The radiation facility 218 comprises an internal volume of 1,370 cubic feet and thus provides a hold-up time which, due to the gas velocity and the volume of the radiation facility, is equivalent to 12 hours. This hold-up time in combination with that furnished by a hold-up cooler 262 presently to be described is sufficient to permit substantially complete decay of many of the short-lived fission product gases. The heat developed as a result of radioactive decay within the radiation facility 218 is suitably removed by cooling water supplied thereto by means of conduits 220 and 222. The radiation facility 218 can be employed for irradiating food or for other industrial purposes as desired. In the event that use of the irradiation facility 218 is not desired, the same can be bypassed by means of a valved conduit 224.

The output of the irradiation facility 218 or of the mist collector 204, as the case may be, is conveyed through a conduit 226, in this example, to a pair of alternatelyoperated cold traps 22% and 230 (FIG. 3A). The cold traps 2-28 and 230 are refrigerated by means of a cooling unit 232 and associated respective cooling coils 234 and 236. Suitable valves 238 and 249 are provided in the inlet conduit 226 and in the cooling coil circuit respectively in order that one of the cold traps 223 or 230 can be isolated from the system as desired. A refrigerant is circulated through the cooling coils 234 and 236 and the unit 232 by means of a suitable compressor 242.

To regenerate or defrost the cold traps 228 and 230, a small portion of the steam leaving the recombiner heat exchanger 158 is bled oft periodically through conduit 172 and a valved conduit system 247 (FIGS. 3A and 3B) to the upper ends of the cold traps 228- and 230. The regenerating steam is then condensed while melting the for approximately 36 hours.

accumulated D 0 ice during its passage downwardly through the isolated cold trap 228 or 230. The liquid issuing from the cold traps 22S and 23% is conveyed through valved conduits 244 and. another conduit 246 to the low pressure storage tank 130. The liquid deuterium oxide thus reclaimed by the cold trap 228 or 230 and returned to the low pressure tank amounts to slightly less than the 0.136 pound per minute conveyed to the cold traps 228 and 230 and is conducted to the low pressure storage tank 1% at a pressure of 35 p.s.i.a. and at a temperature of 32 F.

The uncondensed gases are carried from the cold traps 228 and 230, at a pressure of 25 p.s.i.a. and a temperature of 32 F., through a valved overhead conduit 248- to a dual absorption drier unit 250. The dual absorption drier 250 is a conventional unit wherein any remaining deuterium oxide vapor is removed by means of silicate gel or the like. The heat of radioactive decay is removed and the steam evolved when the drier 25% is regenerated is condensed by cooling water supplied to the absorption drier by means of conduits 252 and 254, while the heat required to remove subsequently the absorbed D 0 from the silica gel is supplied by means of a 0.8 kilowatt electric heater (not shown) connected to the electric leads 256. The system pressure is removed for purposes of regeneration by venting the drier through a valved conduit 257 to a stack 3M- and blower 22 6, presently to be described. The D 0 removed by the absorption drier 25%) is conducted through a valved outlet conduit 258 and a pump 26d to the conduit 246 and thence to the low pressure D 0 storage tank 180.

The gaseous output of the dual absorption drier 250 with the valuable D 0 vehicle now virtually removed completely is conducted by means of a valved conduit 259 to the suction side of a blower 261. By means of the blower 261 the fission product gases and the aforementioned carrier gas are conveyed to the hold-up cooler 262 through a conduit 264. The head developed by the blower 261 and the energy released by radioactive decay of the fission product gases are sufficient to raise the fission and carrier gases to a temperature and pressure of 210 F. and p.s.i.a., respectively, at which conditions the gases enter the hold-up cooler 262. The hold-up cooler 262 comprises, for example, a tank or a length of relatively large size pipe having sufficient volume to delay or hold up the fission product gases conducted thereto The total gaseous volume of the hold-up cooler required for this purpose is about cubic feet. The hold-up cooler 262 is provided with suflicient water cooling, which is introduced through conduits 266 and 268, respectively, to maintain the effluent gases at a temperature of less than 122 F. and a pressure of S0 p.s.i.a. This temperature is selected for the operating temperature of the charcoal beds presently to be described as the minimum temperature attainable with readily available cooling water during the summer. Lower temperatures are practically attainable during the greater part of the year, but these cannot be considered for design purposes. It is desirable, however, to operate the hold-up cooler 262 at the lowest temperature possible under existing weather conditions, in order to secure maximum hold-up time for a given Weight of influent gases and to obtain a maximum adsorbing capacity in the charcoal tanks presently to be described.

A indicated heretofore, the reactor system described in FIGS. 1 and 2 of the drawings is adapted for operation with a total thermal output of approximately 550 megawatts, at which power level a considerable proportion of the deuterium oxide vehicle is radiolytically dissociated. The aforesaid palladium catalyst induces internal recombination in this arrangement of approximately of the radiolytically separated deuterium and oxygen gases, with the remaining 10% of the deuterium and oxygen being employed to sweep the gaseous fission products out of the primary reactor system. In the case of the afore- 15 described quasi-homogeneous reactor employing a slurry with the composition described previously, the following gaseous fission products are released directly during one day of reactor operation:

TABLE I Direct Yield Gaseous Fission Products Released During One Day of Reaction Operation [Reactor power equals 550 MW. 10% external recombination] Total Isotope Half-life production MEV yield activity gmJday Stable '1, 2 Stable, 1.9 h l 1. 77 032 2. 62 4. 26 9. 31 '2. 0 0.57 5. 19 0. 22 4 01 140. 18 Total krypton 35. 78

It may be pointed out that not all of the isotopes and isomers tabulated above result directly from the fission process. For an example, a radioisotope of iodine 1 which is a solid, is produced directly upon fission of the U or U isotopes and then undergoes beta decay with a half-life of 6.7 hours to its daughter isotope, Xe which, of course, is a gaseous material.

The hold-up cooler 262 and the radiation facility 218 are designed as aforesaid to provide a total hold-up time of 48 hours. This time is suflicient to eliminate substantially all of the radioactivity due to the shorter-lived isotopes indicated in the foregoing Table I. Thus, it is seen 15 The charcoal bed adsorption system presently to be described is designed so that the total activity of the discharged Xenon isotope-s does not exceed 2.0% of the Kr activity. The total activity discharged is thus limited to approximately 450 curies per day. However, by .means presently to be described, the non-adsorbed krypton 85 isotope, with the other krypton isotopes can be recirculated through the gas handling system in order to avoid discharging this gas to the atmosphere in the event of adverse Weather conditions. Inasmuch as neutronic capture cross sections of the kryqaton isotopes are negligible, a relatively large quantity of these isotopes can be recirculated through the reactor system Without causing undue parasitic absorption of neutrons. This recirculation also serves to provide additional hold-up time for the short-lived krypton isotopes which are tabulated in Table I and which are relatively non-adsorbed by the charcoal beds presently to be described.

The Xenon adsorption cycle in this example, utilizes three activated charcoal beds or tanks 270, 272 and 274, and an additional charcoal tank 276 is furnished as a spare. However, it will be apparent as this description proceeds that a lesser number of beds can be employed, if desired. Each tank, therefore, is provided with suiticien-t capacity for adsorbing xenon isotopes produced dur ing a period equal to one-half the total time required for both the operations of radioactive decay and of stripping or regenerating the charcoal bed. The efiluent gases of the hold-up cooler 262, which have been cooledas aforesaid to 122 F., are conveyed at a pressure of p.s.i.-a through a conduit 278 to a series of valved conduits 280 coupled respectively to the charcoal beds 270, 272, 274 and 276.

At the end of the long hold-up time required, the only significant activities are those due to Xe and K11 For the system of three charcoal beds, one may therefore analytically determine the optimum relationship between the stripping or regenerating period and the time required for the decay portion of the cycle: let

t =length of stripping portion of cycle (days), t =length of decay portion of cycle (days), then,

from the following Table II that only three gaseous iso- N =N of atoms of X present on b d at b i i topes have intermediate or long half-lives and have sub of decay perigd stantial activity remaining after a period of 48 hours, N =No. of atoms of Xe present on bedat end of decay namely, Xe Xe and Kr period TABLE II Energy Released by One Duys Production of Those Fission Products Found in Adsorption Beds as a F unction of Time After Fission Energy released (MEV/dayX 1013) Isotopes 4 hrs. 12 hrs. 48 hrs. 240 hrs. 1200 hrs.

By proper hold-up of these fission gases, substantially all activity except that due to Kr can be removed. The removal of the Kr activity is, of course, not feasible in this fashion due to its half-life of 10.4 years.

t=decay constant at the end of the decay period:

Differentiating this expression with respect to t and setting the derivative equal to zero, those of t and 1 whichrninimize .the activity discharged are obtained:

( 1=K 3 t2=%=17.3 days (for Ke Using this relationship, the decay period required to reduce the Xe activity to 20% of Kr activity, is determined. The 20% figure is small enough so that the Xe does not make a large contribution to the total activity, yet large enough so that an excessively large adsorption bed is not required.

Allowable Xe activity=89.3 curies/day=2.9 10 disintegrations day/ day.

where N =maxirnum number of atoms of Xe discharged through stack per day.

Now the total number of atoms of Xe present on the adsorption bed at the end of the decay period is given by N multiplied by the time of stripping so that r=( 1 Combining Equations 1 and 7 where t =adsorption time (10) 13.16( 17.3) X l 7=.l34 10 (1-e-" (ea- Equation 10 may be solved for since iii-i is=adsorption time: =53.3 days The total adsorption time shown by Equation 11, or about 54 days illustrates the optimum condition for operation of the charcoal bed arrangement to permit adequate adsorption and decay of the radioactive Xenon isotopes.

In order to determine the maximum heat removal requirements in the fission product adsorption tanks 270, 272, and 274, an estimate was made of the decay heat of radioactive Xe, Kr and their daughters. If the gases are held up for more than four hours before entering the adsorption tanks, those fission product decay chains where the direct product of fission has a half-life of five minutes or less may be ignored for purposes of these calculations. Of the remaining gaseous isotopes, only the parent and the first daughter are considered.

The energy emitted per day by a direct product of fission is calculated by 12 E=EKAQBM where:

E=Energy emitted in rnev./ day t=tirne in hours after fission e=average energy per disintegration A ==number of atoms released into gas stream per day (at 10% external recombination) The energy emitted per day by a daughter isotope is obtained from:

Where the subscript A refers to the parent and B to the daughter.

' The contributions of the various fission products, as a function of time after fission, are given in Table II.

These data have beeen converted to terms of B.t.u./ hr. per gram of gaseous fission products and are plotted in FIG. 5 of the drawings. The data have been employed in calculating the quantity of cooling water required for the radiation facility 218, the hold-up cooler 26-2 and of the charcoal tanks 27%, 272 and 274 throughout the various portions of their operating cycle. In the latter case, assuming that charcoal tank 270 is being operated during the adsorption portion of its cycle approximately 4 Btu. per minute of heat must be removed therefrom. Thus, in the decay portion of the cycle as presented by tank 2'72 the average rate at which heat must be removed is 284 Btu. per minute, and during the regeneration portion of the cycle represented by tank 274, an average of 140 Btu. per minute is generated, which is utilized for maintaining the latter tank at a suitable stripping temperature.

During the progress of the fission product gases through the irradiation facility 2-18, the adsorption drier 25d and the hold-up cooler 262, these gases have been held up for :a time sufficient toallow the short-lived krypton isotapes to decay to such low values that the remaining krypton activity is substantially that due to 141*, which has a half-life of 10.4 years. Hence the Kr may safely be discharged to the atmosphere without further holdup. The charcoal tanks 270, 2.72, 274 and-276 therefore are designed so that they will adsorb the xenon isotopes but will allow most of the Kr to pass through. The charcoal adsorption tanks are operated at an average temper; ature of 122 F. as aforesaid, and in this arrangement each one is capable of holding 54 days of xenon produc- Ition.

As shown by :a reference to FIGS. 3 and 40f the .drawings, while one of the charcoal tanks, for example, 270- is on the adsorption portion of its cycle, two others of the charcoal tanks, for example, 272 and 274 are operated on the decay and regeneration portions of the cycle while the fourth tank 276 serves as a spare.

If the fission product gases are not recirculated through the charcoal tanks in the manner presently to be described, their hold-up time would be due principally to the hold-up cooler 2 72 and the irradiation facility 218 ora total of about two days. After this time the krypton activity (Table II) inexcess of that due to the 10.4,year krypton 85 is substantially nil, and under favorable Weather conditions can be vented in controlled amounts to the atmosphere. However, under certain weather conditions, as noted heretofore the radioactivity of Kr -is too high to be discharged to the atmosphere. In case of inclement weather, then, the charcoal tanks would have to be design-ed to adsorb the krypton isotopes, and for each sank an additional 615 cubic feet of charcoal would activity is accomplished, the additional adsorbing capacity would be provided to hold up the Kr for a period equivalent to the longest anticipated adverse weather con ditions in the area of the nuclear plant. Obviously, however, the length of such adverse weather conditions cannot be determined with any great degree of accuracy. As an alternative, the radioactive gases simply can be permitted to back up or accumulate in the off-gas or gas handling system without venting or other disposal. The latter method, although feasible, for a limited time, eventually causes Xe to be fed back into the primary reactor system where the Xe of course, would parasitically absorb thermoneutrons. The resultant loss in neutrons .19 would require the addition of nuclear fuel or eventually would terminate the chain reaction. By holding and recirculating the fission product gases, smaller charcoal tanks 270 to 2-76 can be employed. and. can be designed'for adsorption of only the xenon isotopes. The recirculation arrangement, presently to be described in greater detail, provides an equavilent hold-up time for the shortlived krypton isotopes in comparision with that. alforded to the xenon isotopes when adsorbed in the charcoal beds. The size of the charcoal tanks noted heretofore are calculated from the following considerations as to heat evolution, volume of beds; bed temperature, tube diametenbed configuration and pressure drop:

HEAT EVOLUTION .Tlie xenon production rateinathe reactor at fullpower is2..22 lb.-mo1s/min. or

Ib.-m=oIes'/cye1e; The decay heat from gaseous fission products is givenby 20' 360 and 362, respectively, of FIG. 7, which curves are plotted against temperature in degrees Centigrade.

'; denoted by points 364 and 365, respectively.

Two conclusions are drawn from this very large decay heat rate. ('1) Cooling the beds by refrigeration is not feasible. ('2) A hold-up period before the gases are admitted to the beds is desirable. The decay of short-lived isotopes in a hold-up cooler and the corresponding reduction of decay heat generation in the beds will allow the charcoal beds to be made of larger diameter tubing.

If the hold-up cooler 262 is inserted into the system to provide a total delay time from reactor tobeds of 48 hours and the calculation given in Equation 14 is repeated,

v(1.8) f'where: V =xenon capacity of charcoal,

' cc. (SIP) gm. charcoal ;p,.=partia 1 pressure of xenon, mm. of

K,n are determined, in the case ofxenon, from 'the'cur'ves If the xenon fiowrate. is 222x10- lb./moles/min. and the helium carrier flowrate is constant at 2.08 10* lb.-moles/min. then where:

P=total pressure on the beds, =50 p.s.i.a.

therefore,

P=27.6 mm. of Hg at full power volume of charcoal bed:

Volumetric flowrate of xenon (STP) lengtl1 of cycle I xenon capacity of charcoal volume of charcoal bed, ftfi:

'20) FX359 X28320, X is X 60111113111. 24 V X 4.53 x 30 =1-.os x 10 where:

F=flowrate of xenon, lb.-moles/miu. t =length of operating cycle, days=54 days The bulk density of the bed is 30 lb./ft.

For the conditions noted heretofore, Equation 20 gives:

The volume of each charcoal bed in this arrangement desirably is set at 20 ft. to provide a factor of safety.

TUBE DIAMETER The temperature operating conditions and the volumetric heat production rate determine the maximum allowable pipe. diameter.

The diameter of each tube in the bed can be found from the equation,

T ==50 C.=l22 F.

Substituting in Equation 17,

Diameter of tube must be approximately 0.777" in this arrangement, and the tubing selected is /a inch BWG18.

BED CONFIGURATION AND PRESSURE DROP The length of tubes, the number of tubes/ bed, and the pressure drop through the oed may now be determined. It

R=volumetric gas rate, ftfi/min. a=cross-sectional area/ tube, ft. tube N :number of tubes V=volurne or' beds:20 ft. L=length of beds, ft.

v=gas velocity, ft./min.

For /3" B'WGlS tubing, a=(l.00329 ft /tube. If L is taken as 2% it. (standard commercial length), then Equation 23 gives:

it has been found that the pressure drop through the charcoal bed is negligible.

Based upon the considerations outlined above each charcoal bed 27%, 272, 274 and 276, in this example, ineludes a shell {not shown) having a total of 307 tubes, each twenty feet in length, arranged therein in a spaced array in order to afford cooling water passages therebetwcen. Conventional manifolds or tube sheets (not shown) are secured to the respective ends of the tubes to couple all of the tubes into the carrier gas system presently to be described,

Referring now to FIG. 4 of the drawings, one method of operating the charcoal tanks 276, 272 and 274 is shown graphically. The pair of vertical lines 232 represent the point at which the reactor 2i begins power operation, and is taken as zero time for purposes of this graph. The single vertical lines 234 each represent a complete cycle of adsorption, decay and regeneration as applied to any one of the charcoal tanks which cycle equals, in this example, a total of 162 days. Each 162 day cycle is subdivided into increments of 54 days each as indicated by the reference character 236. The horizontal lines 270, 9372 and 27d correspond to the charcoal tanks illustrated in FIG. 3.

At the beginning of reactor operation, the charcoal tank 276 is coupled to the hold-up cooler 26?. by opening valve 283 in the associated one of the conduits 2% and to the carrier gas recycling system, presently to be described,

by opening valve 323 (HG. 3A). The tank 275i is then maintained in the adsorption portion of its cycle for a 54-day period while the remaining of the tanks 2.72, 274 and Z76 are decoupled from the system by shutting off the associated valves Bfiil and 3W2, and 2Z--329, Z94--33l and 2i5-333, respectively. At the end of the first 54-day period, the charcoal tank 27% is decoupled from the hold-up cooler 252 and the recycling system by closing the valves 2&3 and 323, and then proceeds to the decay portion of its cycle, which in this example, is 98.5 days as represented by arrow 2% (FIG. 4). At the same time, the tank 27?. is coupled to the hold-up cooler 2623 and into the carrier gas recycling system by opening its associated valves til-2 and 329 in order to initiate the adsorption portion of its cycle. At the end of the second 54-day increment, the third charcoal tank 27 4 is coupled into the aforesaid system by opening its associated valves 2% and 331. At the same time the second tank 272 is ecoupled entirely from the system for the decay portion of its cycle. Seventeen and one-half days before the end of the third 54-day increment, the decay period of the first charcoal tank 27% is terminated and the charcoal contained within this tank is regenerated by drawing ventilation air through the charcoal tank 27s by means of the stack blower 296 after opening respective ones of the groups or" valves 3% and 3632.

The ventilation air also serves to dilute the activity of the stripped gases to acceptable concentrations for venting to the atmosphere. This ventilation air is supplied to and withdrawn from the charcoal tanks by means of conduit systems 2%, Sill and 2%, respectively. The ventilation air, which is collected from the nuclear reactor plant, is first conducted to a dust filter 2% through conduit 335, or the like, and thence to selected ones of the charcoal tanks 279, 272 and 2'74 by opening appropriate ones of the valves 3% and 3%. Regeneration of the charcoal contained within each tank is attained by reducing the cooling water normally supplied to the charcoal tanks by closing the associated one of the valves 3ll3 in the cooling water system. The heat developed by residual radioactivity at the end of the decay cycle of 90.5 days, or about 140 Btu. per minute as indicated heretofore, is suflicient to raise the charcoal to a temperature of about 212 F. at which the adsorbed Xenon isotopes are removed from the charcoal and subsequently are carried to the stack Sti lby the blower 2% through the conduit system 351 1 and 2% and stack inlet conduit 3%. The ventilation air thus serves to flush the stripped xenon isotopes and residual portions of krypton and the helium or other carrier gas described heretofore, out of the charcoal tank being regenerated. Any ventilation air not required for regenerating one of the charcoal tanks is conducted to the suction side of the stack blower 296 by means of ventilation air by-pass conduit 3&5.

In a similar manner, any gaseous fission products removed by the chemical processing plant 1% (FIG. 2) are conducted to the cold trap inlet conduit 226 through conduit 112 (E68. 2 and 3A). From this point the ettluent gases of the chemical processing plant 1&6 are treated as explained heretofore in connection with the eli'luent gases of the irradiation facility 218 or of the mist collector 2%. The processing plant gases are added at this point in the gas handling system inasmuch as these gases may contain residual amounts of valuable D 0 vehicle, in this case.

As indicated heretofore, the radioactivity due to the longest-lived of the adsorbed Xenon isotopes, which at the end of the decay cycle of 90.5 days is principally l'iie is approximately 20% of the activity due to the relatively non-adsorbed 141- isotope contained within the charcoal tank 270. Thus, the heat required to regenerate the charcoal is furnished by decay heat of the adsorbed Xe isotope and the residual Kr At the end of the regeneration portion of the cycle, which is indicated by the reference character 3% (FIG. 4), the charcoal tank Zitl is again prepared for the adsorption portion of a subsequent operating cycle. In a similar manner, the charcoal tanks 272 and 274 are alternately operated through the cyclic functions of adsorption, decay and regeneration, as explained heretofore.

in this arrangement of the invention, the stack 304 is approximately 250 feet in height above ground level, which height is sufficient to reduce by diffusion the activity of those fission product gases eliminated from the top of the stack to acceptable levels at a point on ground level at the base of the stack. However, the activity level of the fission product gases at the month 310 of the stack is approximately times that of accepted standards. In the event of adverse weather conditions, such as a temperature inversion at which time it would be virtually impossible to eliminate the fission product gases to the atmosphere, due to the then inadequate dispersion of the gases, the spare charcoal bed 276 provides a minimum additional adsorption time of 54 days for the xenon isotopes, which would be more than adequate to meet any unexpected climatic condition. A valve 312 is provided adjacent the suction side of the stack blower 296 to control the rate of flow to the stack 364 and consequently the level of radioactivity discharged to the atmosphere.

Referring once again to FIGS. 3A and 3B of the drawings, means are illustrated therein for recycling the aforementioned helium carrier gas through the selected one of the charcoal tanks, which at a given time is being employed for the adsorption portion of the operating cycle, and back to the carrier gas storage tank 194. From the helium storage tank 194 which in this example is maintainedv under a pressure of 2000 p.s.i., the helium carrier gas is applied to the high pressure deuterium oxide storage tank 160 through a valved conduit 320 in order to preserve the desired operating pressure of 2000 p.s.i. therein.

A second function of the carrier gas storage tank 194 is to supply make-up carrier gas through conduit 192 and pressure letdown valve 334 (FIG. 33) to the recombiner condenser 174. In the recombiner condenser the carrier gas, which is recycled thereto as described subsequently, is mixed with the contents of the recombiner condenser 174 and exits therefrom with the unoondensed gases via conduit 206. The use of the carrier gas in this fashion minimizes the solution of the fission product gases in the condensed deuterium oxide leaving the recombiner condenser 174 for storage in the low pressure deuterium oxide tank 180.

From the recombiner condenser the gaseous fission products and the helium or other carrier gas are conducted through subsequent components as described heretofore to that one of the charcoal tanks 270 to 276, which at that time is being operated on the adsorption portion of its cycle, for example, the tank 270. From the adsorption charcoal tank 270, the carrier gas and the nonadsorhed gaseous fission products are returned through the associated one of valved conduits 322 (FIG. 3A), a common conduit 324 (FIGS. 3A and 3B), and the conduit 192 to the recombiner condenser 174. A check valve 326 (FIG. 3B) is provided in the conduit 324 in order to prevent accidental reverse flow of pure carrier gas from the storage tank 194.

The conduits 322 are provided with valves 328, 329, 331 and 333, respectively, in order to isolate the charcoal tanks, for example, tanks 272 and 274, which at this time. are being operated on the decay and regeneration portions of their adsorption cycles and also the spare tank 276, from the circulating carrier gas system. In this example of the invention, approximately .05 pound per hour of carrier gas is circulated through one of the charcoal tanks and back tov the recombiner condenser 174. The carrier gas and fission products leave the recombiner condenser 174 at a pressure of 35 p.s.i.a., which falls to 20 p.s.i.a.v after being cooled in the cold trap 228 or 239. The blower 261 is then employed to increase the pressure of gases entering the charcoal tank to 50 p.s.i.a. The recirculating carrier gas and non-adsorbed fission products decrease in pressure to 35 p.s.i.a. when returned to the recombiner condenser 174 due to pressure drops occasioned by the charcoal tank and flow control valve 327' in the inlet conduit 192.

During normal reactor operation, a small portion of the total flow is withdrawn from the recirculating carrier gas circuit. through aconduit 33% and valve 332, coupled therein to the suction side. of the stack pump 296. Thence, the carrier gas. andcirculating fission gases bled from the conduit 324 are vented to the stack 304. At the same time an equivalent amount of carrier gas is fed from the storage tank 194: to the recombiner condenser 174 via conduit 192 and pressure letdown valve 334. The recycled carrier gas thus'is purified continuously by these bleed and feed arrangements. In this manner the concentration of non-adsorbed fission product gases within the recycled carrier gas stream is maintained at an acceptable or predetermined level.

If the bleed rate is 1% of the total volume recirculated, the concentration of fission product gases within the recirculating helium system can be increased about one hundredfold over that which would obtain were the carrier gas not recycled.

Inasmuch as the charcoal tanks 270 to 276 are designed primarily for the adsorption of the xenon isotopes, the concentration of fission products within the circulating helium system comprises primarily the relatively nonadsorbed krypton isotopes. Accordingly, should any of these recirculated isotopes be returned to the primary system, for example, in a manner presently to be described, the power level of the primary system will not be eiiected due to the absence of isotopes having a high neutronic capture. cross section, particularly xenon 135. The pressure letdown valve 334, coupled to one output conduit 192 of the helium storage tank 194, is operated when the pressure of the recycling carrier gas system falls below a predetermined level, which in this example is 35 p.s.i.a.

When one of the charcoal tanks 27!) to 276 has complete-d its adsorption period, another of the tanks is coupled to the conduit 324 and thence to the circulating helium system, by suitable operation of the associated valves 328, 329, 331 or 333. In. this manner continuous adsorption and subsequent decay of substantially all of the xenon isotopes is provided. However, inasmuch as the majorportion of the krypton isotopes are not adsorbed by the charcoal tanks, substantial radioactive decay of the short-lived krypton isotopes for example, Kr, the Kr isomer (4.4 hrs.), Kr Kr, etc., is ensured in this example by recirculating continuously these isotopes together with the carrier gas through the adsorbing charcoal tank, the conduit 324 and associated components for such length of time that all of these short-lived krypton isotopes substantially are decayed. The necessary hold-up time is accomplished by permitting the total gaseous fission product concentration within the circulating carrier gas system to increase as aforesaid over the concentration which would obtain were the carrier gas employed on a once-through basis. The longest-lived krypton isotope, Kr isomer having a half-life of 10.4 years, obviously cannot be permitted to decay in this fashion due to the tremendous length of time involved; and this isotope is gradually removed as aforesaid from the recirculating carrier gas system by means of the bleed conduit 330 and associated components, from which it is connected to the stack 304 and vented to the atmosphere.

In the event of any contingency, including inclement weather conditions such as a temperature inversion, during which it is highly undesirable to vent the radioactive gases in this fashion, the bleed valve 332 can be closed and the longest-lived krypton isotope Kr can be permitted to accumulate within the circulating helium system. In the event that the valve 332 must be kept closed for an extended time, the increasing concentration and resultant pressure of the non-adsorbed krypton isotopes will eventually cause the krypton isotopes to be dissolved in the condensate leaving the recombiner condenser 174, whereby increasing amounts of krypton isotopes are circulated back to the primary reactor system. From this point in the system, the accumulating non-adsorbed isotopes are carried to the circulating loop 74 of the primary reactor system by way of the normal liquid vehicle return to the primary system via the recombiner heat exchanger 158 and associated components, in the manner described heretofore. As stated above, none of the krypton isotopes produced in the chain reaction have more than negligible neutronic capture cross sections and, therefore, accumulation of. krypton isotopes in this fashion will not materially a'ttect the reactor power level. l

' On the other hand, the xenon isotopes, particularly Xe should not be returned to the primary reactor system in any event due to their much higher neutronic adsorption cross sections, and therefore, it is desirable that the Xenon isotopes be extracted continuously from the circulating carried gas system. This is accomplished in the manner described heretofore by means of the charcoal tanks 270 to 276, and adequate decay time for the Xenon isotopes, which are all relatively shortor intermediate lived, is provided by the cyclic operation of the charcoal tanks. In case of inclement weather conditions or other contingency, the spare charcoal tank 276 performs a similar function in the case of the xenon isotopes by providing additional adsorption time amounting to a minimum of 54 days and subsequent decay time, in the manner described heretofore. In this event the spare tank 276 can be coupled into the circulating carrier gas system, by opening valves 2% and 333, such that the spare tank replaces that one of the tanks which cannot be regenerated at this time.

In FlGS. 6 and 600i the drawings a pictorial fluid circuit diagram is presented which indicates more or less quantitatively the flow streams associated with components of the aforedescribed recirculating carrier gas systern. From the legend 349 (FIG. do) it will be seen that the gas stripped from the charcoal tank 274, as indicated by the stream 342 and flow arrow 344, when the tank 274 is being regenerated, consists substantially of Xenon isotopes with a relatively large quantity of ventilation air (not shown). On the other hand that stream of the carrier gas system, indicated by the reference character 346 and circulating through the adsorption charcoal tank 27% consists entirely of krypton isotopes and the carrier gas. A minor portion of this stream 346 is normally diverted. as shown by stream 348 and flow arrow 35b to the stack Sti l, The loss of carrier gas in this manner, which as aforesaid is a small fraction of'the total fiowthrough the'carrier gas system, is made up from the storage tank 1% to the recombiner condenser 174 as denoted by the flow arrow 3%. The flow between the carrier gas tank 194 and the condenser 174 is shown by the conduit 352. The major proportion of the carrier gas and non-adsorbed gaseous fission products leaving the adsorption bed 27% is conveyed back to the recombiner condenser 174, as indicated by stream 356 and flow arrow 353, as explained more fully in connection with FIG. 3.

From the foregoing, it will be apparent that a novel and eflicient radioactive gas handling system has been disclosed herein. Although the invention has been described primarily in connection with a quasi-homogeneous type reactor, it will be obvious that this arrangement can be applied to any known reactor system from which fission product gases are evolved during reactor operation. The slight differences which may occur in material balance between the xenon and krypton fission gases due to the power level of the reactor and to the type of fissionable isotope can be adjusted readily by application of the considerations noted heretofore. By the same token, the principles of the invention disclosed herein can be adapted also for use with a plutonium reactor, with the type and quantity of adsorbing agent being adjusted to the charactor of fission product gases resulting from plutonium fission. It will also be appreciated that the present invention can be adapted for separating or permitting radioactive decay of any relatively short-lived radioactive iiuid materials, such as that evolved from a clad-fuel processing plant, or the like. 'It is to be understood, furthermore, that the reactor system parameters, including those associated with the off-gas system of the invention, and other descriptive matter employed herein are presented only for purposes of illustrating the invention. Such descriptive matter, then, is not to be construed as limitative of the invention. For an example, as pointed out heretofore, the type and quantity of radioactive gases and the amption material for which the gas-handling system of the invention is utilized can be varied readily without departing from the teachings thereof.

Accordingly, numerous modifications of the invention will occur to those skilled in the art wtihout departing from the spirit and scope of the invention. Moreover, it is to be understood that certain features of the invention can be utilized Without a corresponding use of other features.

Accordingly what is claimed as new is:

1. A gas-handling system adapted for use With a nuclear reactor system, said gas-handling system including a plurality of gaseous fission product adsorption tanks, means for separating gaseous fission products from said reactor system, means for coupling said separating means to said reactor system and to selected ones of said adsorption tanks, means for selectively recirculating a carrier gas through said separating means and through at least one of said adsorption tanks to aiiord additional holding time for said products, said adsorption tanks containing an adsorbent material capable of adsorbing a portion of said fission products, the remainder of said fission products being accumulated within said carrier gas recirculating means.

2. A gas-handling system adapted for use with a nuclear reactor system, said gas-handling system including a plurality of gaseous fission product adsorption tanks, means coupled to said reactor system for separating gaseous fission products therefrom, means for coupling said separating means to said reactor system and to selected ones of said adsorption tanks, means for selectively recirculating a carrier gas through said separating means and through at least one of said adsorption tanks to afford additional holding time for said products, said adsorption tanks containing an adsorbent material capable of adsorbing a portion of said fission products, the remainder of said fission products being accumulated within said carrier gas recirculating means, and a conduit system for coupling selected ones of said adsorption tanks to means for venting said adsorbed fission products.

3. A gas-handling system adapted for use with a nuclear reactor system, said gas-handling system including a plurality of gaseous fission product adsorption tanks, means coupled to said reactor system for separating gaseous fission products therefrom, means for coupling said separating means to said reactor system and to selected ones of said adsorption tanks, means for selectively recirculating a carrier gas through said separating means and through at least one of. said adsorption tanks to afford additional holding time for said products, said adsorption tanks containing an adsorbent material capable of adsorbing a portion of said fission products, the remainder of said fission products being accumulated within said carrier gas recirculating means, means for venting said adsorbed and non-adsorbed fission product gases, a valved conduit system for coupling selected ones of said adsorption tanks to said venting means, and a valved conduit coupling said carrier gas recirculating means to said venting means.

4. A radioactive fiuid separating system, the combination comprising a plurality of adsorption tanks, said tanks each containing an adsorbent material capable ofi adsorbing selected ones of said radioactive fluids, means for selectively recirculating a carrier fluid and said radioactive fluids through at least one of said adsorption tanks to afiord additional holding time for said radioactive fluids, means for regenerating selected ones of said adsorption tanks to remove said adsorbed fluids, means for isolating selected ones of said adsorption tanks from said fluid handling system to permit decay oh the radioactive fluids adsorbed therein, and a bleed and feed purification system coupled to said recirculating means for removing at least a portion of the non-adsorbed radioactive fluids accumulated within said recirculating means.

5. A radioactive fiuid separating system, the cornbination comprising a plurality of adsorption tanks, said tanks each containing an adsorbent material capable of adsorbsesame ing selected ones of said radioactive fluids, means for selectively recirculating a carrier fluid through at least one of said adsorption tanks to afford additional holding time for said radioactive fluids, means for regenerating selected ones of said adsorption tanks toremove said adsorbed fluids, means for isolating selected ones of said adsorption tanks from said gas-handling system to provide in combination with said recirculating means adequate time for decay of at least a portion of the radioactive fluids. contained therein, disposal means for said radioactive fluids, means for stripping said adsorbed radioactive fiuids from selected ones of said adsorption tanks, a conduit system connecting selected. ones of said adsorption tanks, a conduit system connect ng selected ones of said adsorption tanks to said disposal means, and a bleed and feed purification system coupling said recirculating means, respectively, to said disposal means-and to a source of said carrier fluid.

6. A gas-handling system adapted for use with a nuclear reactor system, said gas-handling system including a plurality of gaseous fission product adsorption tanks, means for separating gaseous fission products from said reactor system, means for coupling said separating means to said reactor system and to selected ones of said adsorption tanks, means for selectively recirculating a carrier gas through said separating means and through at least one of said adsorption tanks to aiford additional holding time. for said products, said adsorption tanks containing an adsorbent material capable of adsorbing a portion of said fission products, the remainder of said fission products being accumulated Within said carrier gas recirculating means, and a bleed and feed purification system coupled to said recirculating means for removing at least a portion of the non-adsorbed radioactive gases accumulated within said recirculating means and for adding an equivalent amount of relatively pu-re carrier gas from a source of said carrier gas.

7. A. radioactive. gas separating system for use with a source of said gas, said system including a plurality of radioactive gas adsorption tanks, means for separating radioactive gas from said source, means for coupling said separating means to said source and to selected ones of said adsorption tanks, means for selectively recirculating acarrier gas through said separating means and through at least one of said adsorption tanks to afiord additional holding time for said radioactive fluid, said adsorption tanks each containing an adsorbent material capable of adsorbing a portion of, said radioactive gas, the remainder of said radioactive gas being accumulated Within said carrier gas recirculating means, and a purification system. coupled to said recirculating means for removing at leasta portion-of the non-adsorbed radioactive gas accumulated Within: said recirculating means and for adding an equivalent amount of relatively pure carrier gas from a. source of said carrier gas.

References Cited in the file of this patent UNITED STATES PATENTS lPatrick et a1. Mar. 30 I920 2,157,565 Pexton et al. May 9, 1939 2,635,707 Gilmore Apr. 21, 1 953 2,675,089 Kahle Apr. 13', 1954 2,770,591 Wigner et al Nov. 13, 1.956 2,825,688 Vernon- Mar. 4, 1958 OTHER REFERENCES, 

1. A GAS-HANDLING SYSTEM ADAPTED FOR USE WITH A NUCLEAR REACTOR SYSTEM, SAID GAS-HANDLING SYSTEM INCLUDING A PLURALITY OF GASEOUS FISSION PRODUCT ABSORPTION TANKS, MEANS FOR SEPARATING GASEOUS FISSION PRODUCTS FROM SAID REACTOR SYSTEM, MEANS FOR COUPLING SAID SEPARATING MEANS TO SAID REACTOR SYSTEM AND TO SELECTED ONES OF SAID AABSORPTION TANKS, MEANS FOR SELECTIVELY RECIRCULATING A CARRIER GAS THROUGH SAID SEPARATING MEANS AND THROUGH AT LEAST ONE OF SAID ADSORPTION TANKS TO AFFORD ADDITIONAL HOLDING TIME FOR SAID PRODUCTS, SAID ADSORPTION TANKS CONTAINING AN ADSORBENT MATERIAL CAPABLE OF ADSORBING A PORTION OF SAID FISSION PRODUCTS, THE REMAINDER OF SAID FISSION PRODUCTS BEING ACCUMULATED WITHIN SAID CARRIER GAS RECIRCULATING MEANS. 